In the art of modular fixturing or tooling systems, it is known to use various grid plates or components which have flat surfaces each provided with a precision X-Y grid pattern of threaded holes and precision bores for conveniently attaching and precisely locating a workpiece to the table of a machine tool. For example, U.S. Pat. Nos. 4,073,215 and 4,310,963 each discloses a system including a base plate or sub-plate having an X-Y grid pattern of threaded holes and precision bores, and the systems are used for securing workpieces to the table of a machine tool. The use of such a modular fixturing or tooling system has been found highly desirable for reducing the set-up time required to secure a workpiece to a machine tool table at predetermined positions depending upon the type of machining required on the workpiece.